Feb 17, 2009

Convert images to greyscale

There are at least a hundred ways of doing this, but I wanted a single-line way to make greyscale versions of a bunch of images on a website I was developing. The last thing I wanted was to load each one in turn into a graphics application to edit the colors.

ImageMagick to the rescue:
for img in *.gif ; do convert $img -colorspace Gray -colors 16 grey_$img ; done

Ok - so not really one line, but almost :-)

And this is what it looks like afterwards in my file explorer:

at

3 comments:

  1. Jabulani18 February, 2009 01:16

    HURRAH!!!!! Another post at last ... looks impressive; I'll ask Luke if it is ;-) Do you think you could write something (as many lines as you like!) that makes chocolate come out of my printer instead of paper?

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  2. Craig Taverner20 February, 2009 14:26

    OK. That was a hard one, but here it is. I figured out how to make nice brown chocolate come out your printer:
    ----------------------------
    %!
    %% Chocolate

    /Times-Roman findfont
    62 scalefont
    setfont

    100 200 translate
    45 rotate
    2 1 scale
    newpath
    20 0 moveto
    (Chocolate) true charpath
    gsave
    0.5 0.3 0.1 setrgbcolor
    fill
    grestore
    0.5 setlinewidth
    0.4 setgray
    stroke

    showpage
    ----------------------------

    OK - I admit I failed to stop the paper coming out with it, but I think with a little more research we can crack that one too :-)

    (P.S. To use the above recipe, simply save the text between the '----' lines to a file called chocolate.ps. Then print that file.)

    (P.P.S. Credits to the ps-tutorial at UWA.)

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  3. Jabulani20 February, 2009 23:13

    See P.S. If this instruction fails, try alternative command:
    call know-it-all-teenage-computer-chappie saying "Luke, do this for me! It's from that very clever bloke in Sweden!" and he'll be here like a shot. Mind you, he'll probably eat the flippin' choccy too! *sigh*
    I'm back to Amadei ...

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